558 



SCIENCE 



[N. S. Vol. XXIX. No. 744 



the east limb of the anticline in Red Mountain 

 near Birmingham is the ore of commercial value 

 at present. Northwest of this valley lies the 

 Warrior Field, containing coking coals, while to 

 the southeast lies the Cahaba Field, containing 

 high-grade steam and domestic coal. Cambro- 

 Ordovician dolomite within the valley and Mis- 

 sissippian limestone between the ore outcrop and 

 the coal fields both afford stone for fluxing. The 

 topography is of the ridge and valley type, very 

 favorable for transportation lines to reach the 

 outcrops of ore, stone and coal. The ore is of 

 sedimentary origin. It contains approximately 

 36 per cent, of iron, 12 to 25 per cent, silica, 8 to 

 20 per cent, lime and .33 per cent, phosphorus. 

 It occurs in beds like coal, but, vmlike coal, the 

 beds are subject to residual enrichment on the 

 outcrop, due to solution of soluble constituents; 

 also they are not so broadly extensive as coal 

 beds. Studies of the strike sections of the ore 

 on the outcrop and of sections at right angles to 

 the outcrop by means of mine openings and drill 

 records show that the beds are long, narrow, lens- 

 like bodies. The quality of the unweathered ore 

 is fairly constant in the direction of the dip. 

 All the facts obtained during recent geological 

 surveys of this field indicate that the ore is the 

 result of original deposition of ferruginous sedi- 

 ments and that, so far as the material continues 

 of workable thickness, it will mostly be found of 

 workable quality. 



The Earthquake Rift in Eastern San Luis Obispo 

 County, California: Ralph Abnold and H. R. 

 Johnson. 



This paper embraced a description of some of 

 the topographic features along the earthquake 

 rift and was illustrated by lantern views showing 

 the terraced aspect of the country adjacent to 

 and the offsetting of streams by the rift. An 

 instance of offsetting was described in detail 

 where a stream flowing southwestward from the 

 Temblor Range strikes the rift at right angles, 

 is directed to a northwesterly course along the 

 rift for 400 feet, and finally leaves the rift at 

 right angles and flows off on the plain. The scarp 

 along the rift at this point is on the northeast 

 side, and there is apparently a small alluvial fan 

 developed where the stream leaves the rift on the 

 southwest, so that any hypothesis other than one 

 in which a horizontal movement of 400 feet is 

 assumed does not seem to explain the conditions 

 found here. 



Philip S. Smith, 



Secretary 



THE PHILOSOPHICAI, SOCIETY OF WASHINaTON 



The 659th meeting was held on January 30, 

 1909, Vice-president Wead presiding. 



The following papers were read: 

 A Proposed Method for Determining the Solar 

 Parallaw: Dr. C. G. Abbot. 

 The author cited the recently published values 

 of the solar parallax obtained by observations of 

 the minor planets, and especially of Eros. These 

 generally agree very closely and yield a value 

 8".80 or a trifle higher. The recent long-continued 

 and careful work of Doolittle, on the other hand, 

 has given the value of the aberration constant as 

 probably 20".51, corresponding with a parallax 

 8".783. Eiistner and Halm have employed the 

 I>6ppler principle to determine the velocity of the 

 earth in its orbit, by observing the displacements 

 of lines in the spectra of certain stars at intervals 

 of six months. Kiistner obtained thereby 8".84 

 for the solar parallax. 



The author proposed to use two coelostats and 

 reflect simultaneously on a powerful spectroscope 

 the light of Venus and Mars. A differential 

 velocity of these objects as great as 28 km. per 

 second is available. Adams has in similar fashion 

 determined the velocity of rotation of the sim 

 with a probable error for a single photographic 

 plate of 0.004 km. per second. An experimental 

 photograph of Venus's spectrum has been made 

 with the tower apparatus at Mt. Wilson, on the 

 same scale employed by Adams for the sun, in 

 two hours' exposure. It is thought that a scale 

 of spectrum one fifth as great can be used in prac- 

 tise for a simultaneous exposure on Mars and 

 Venus. By alternating the two coelostats on suc- 

 cessive nights, and by carefully reducing the light 

 of Venus to equal that of Mars, and by using a 

 long focus telescope to form the images, so that 

 only the central part of the disks of the planets 

 would be used, the author hoped the method 

 would be capable of yielding in ten nights a value 

 of the parallax accurate to one part in 2,000. 

 The Magnetic Properties of Iron: Their Applica- 

 tion and Measurement: Mr. C. W. Bubkows. 



The 660th meeting was held on February 13, 

 1909, Vice-president Wead presiding. The follow- 

 ing papers were read: 

 A New Method for Determination of Focal 



Length: Mr. I. J. Pbiest. 



This method, based on the Fabry and Perot 

 interferometer, gives the focal length directly and 

 accurately; it is adapted to lenses of all focal 

 lengths; it can be used for the determination of 

 achromatism; and finally it is unique in that 



